drm/doc: include xe_drm.h

Make sure the uapi gets picked up by the normal docs build.
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Francois Dugast <francois.dugast@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Francois Dugast <francois.dugast@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Documentation/gpu/driver-uapi.rst

@@ -17,3 +17,8 @@ VM_BIND / EXEC uAPI
     :doc: Overview
 
 .. kernel-doc:: include/uapi/drm/nouveau_drm.h
+
+drm/xe uAPI
+===========
+
+.. kernel-doc:: include/uapi/drm/xe_drm.h